Frequency changing system



Nov. 27, 1934. H MEYER-DELlUS v 1,982,605

FREQUENCY CHANGING SYSTEM Nov. 27, 1934.

H. MEYER-DELIUS FREQUENCY CHANGING SYSTEM Filed June 16, 1935 2 Sheets-Sheet 2 Patented Nov. 27, 1934 PATENT OFFICE FREQUENCY CHANGING' srsrm Heinrich Meyer-Delius, Heidelberg-Schuman, Germany, assigner to Aktiengesellschaft Brown Boveri d: Cie., Baden,

Switzerland, a feint-stock company of Switzerland Application June 16, 1933, Serial No. 676,065 In Germany June17, 1932 14 Claims.

This invention relates to improvements in alternating current frequency converting systems utilizing electron discharge devices, and more particularly to such systems in which a variable amount of in-phase current or of reactive current is to be exchanged in either direction between lines which are not always rigidly maintained in an invariable frequency relation.

It is well known to connect two alternating current lines or two portions of a single alternating current line by a frequency converter comprising an input transformer, an electron discharge device and an output transformer, in which current supplied from one line to the input transformer is rectified and then converted into alternating current by the electron discharge device, and delivered to the second line through the output transformer. By energizing the control electrodes of the electron discharge device in dependence on the frequencies of both the input and the output circuits, the system may be made operable for such energy transfer in either direction between two lines even when the frequency relation between such lines is variable. The controlling means may also be provided with means for adjustment which permit separate regulation of the direction and of the intensity of the flow of inphase current and of reactive current between the lines.

It is, therefore, one of the objects of the present invention to provide a frequencyconverting system utilizing an electron discharge device, the system permitting flow of energy in either direction between two alternating current lines which are not rigidly maintained in an invariable frequency relation.

Another object of the present invention is to provide a frequency converting system utilizing an electron discharge device in which system the 40 direction of the flow of energy between two alternatng current lines which are not rigidly maintained in an invariable frequency relation may be determined by automatically or manually operated control means.

Another object of the present invention is to provide a frequency converting system utilizing an electron discharge device in which system the intensity of ow of in-phase current between two alternating currentA lines, which are not rigidly maintained in an invariable frequency relation, may be determined by automatically or manually operated control means.

Another object of the present invention is toprovide a frequency converting system `utilizing an electron discharge device in which system the (Cl. P12- 281) intensity of flow of reactive current between two alternating current lines, which are not rigidly maintained in an invariable frequency relation, may be determined by automatically or manually operated control means.

Another object of the present invention is to provide a frequency converting system utilizing an electron discharge device and in which the voltage induced in the primary windings of the output transformer may be adjusted in phase and in magnitude with respect to the voltage of the output line by automatically or manually operated control means.

Another object of the present invention is to provide a frequency converting system utilizing an input transformer, a plurality of electron discharge devices and an output transformer, in which each transformer is provided with only two windings.

Objects and advantages other than those above set forth will be apparent from the following description when read in connection with the accompanying drawings in which:

Fig. 1 dlagrammatically illustrates one embodiment of the present invention for converting polyphase alternating currents at one frequency into single phase alternating currents at the same or at another frequency', and in which the flow of inphase current and of reactive current maybe separately regulated both in direction and in magnitude; A

Fig. 2 diagrammatically illustrates the sequence of energization of the control electrodes of the discharge device utilized in the embodiment illustrated in Fig. 1 and the resultant curves representing the output voltage of the system; and

Fig. 3 diagrammatically illustrates another embodiment of the present invention employing two transformers each having only two windings.

Referring more particularly to the drawings by characters of reference, reference numeral 6 designates an alternating current line herein shown as a three phase line only for the reason that such type of line is most frequently used in practice. Line 6 may be energized at any desired frequency but such frequency need not be maintained at a constant value and may present regular or irregular variations in time. In the present embodiments, it is assumed that it is desired to transmit energy between line 6 and a single phase alternating current line 7. It 'will be understood, however, that the system may be made operable to transmit energy to an alternating current line of any desired number of phases by suitable modification of some of the members shown and by suitable duplication of some of suchmembers. The frequency of line 7 may be at any desired value which may be related or unrelated to the frequency of the voltage of line 6. Line 6 is connected with primary winding 8 of'an input transformer having two secondary windings 11 and 12 and line 7 is connected with the secondary winding 16 of an output transformer having a primary Winding 14. Windings 11 and 12 each comprise a plurality of star connected winding portions such as 11a, 12a, etc. severally connected with the sets of anodes such as 21a, 22a, etc. of two electron discharge devices 17 and 19. Device 17 is provided with a cathode 18 and device 19 is provided with a cathode 20 and, in the embodiment illustrated in Fig. 1, the two cathodes are connected with the midtap of winding 14. It will be understood that, in such embodiment, devices 17 and 19 may be replaced by a single device containing sets of anodes 21 and anodes 22. The two portions 14a. and 14h of winding 14 are severally connected with the neutral points of windings 11 and 12.

Device 17 is provided with control electrodes such as 31a and device 19 is likewise provided with control electrodes such as 32a, each of such control electrodes being associated with one of v the anodes 21 or 22. Each control electrode of device 17 is energized over a resistance such as 23 in parallel with one of the control electrodes of device 19 over a resistance such as 27. Each pair of control electrodes is associated with a pair of anodes receiving, from windings 11 and 12 respectively, voltages which are in phase opposition; the anodes and control electrodes being severally associated. All the control electrodes of the electron discharge devices lare generally maintained negative with respect to cathodes 18 and 20 by a battery 24 connected therewith through a resistance such as 26 and resistances such as 23 and 27. The several pairs of control electrodes are sequentially energized at a positive potential with conductive segments such as 33a separated by insulation. The width of each segment is preferablysmall compared to the width of the insulation intervening and spacing the segments to obtain only a momentary energization of each control electrode upon contact of a brush of the distributor with each segment. Distributor 33 is provided with two brushes 34 and 36 which independently engage with each o f the segments without interfering with each other in their rotary motions. Itis convenient to express the speed of the brushes as a number of revolutions per second in definite relation with the frequencies of the voltages in lines 6 and 7 expressed in cycles per second. The speed of brush 34 is then equal to the frequency of the voltage of line 6 plus the frequency of the voltage of line 7 whereas the speed of brush 36 is equal to the frequency of the voltage of line 6 minus the frequency of the voltage of line 7. It will be understood that the same relative motion of brushes 34 and 36 with respect to the segments of distributor 33 could be obtained by causing distributor 33 to rotate at a speed equal to the frequency of the voltage of line 6 and causing brushes 34 and 36 to rotate in opposite directions at a speed equal to the frequency of the voltage of line 7. Brush 34 is driven at the speed defined above by an electric motor having placement of the tap thereon permits adjustment of the distribution of current Within winding 39 and thereby adjusts the position of the rotating field induced bysuch winding with respect to the voltage cycle of line 7. Brush 36 is similarly driven by an electric motor having an armature 42 energized from line 6 and a field 43 connected with line 7 over a resistance 44 provided with a movable tap.

In operation, assuming that lines 6 and 7 are energized at their respective operating frequencies, anodes 21a to 2li of device 17 and-winding portion 14a receive, from the several portions of winding 11, polyphase sinusoidal voltages represented by curves 51a. to 51f plotted in Fig. 2 against a time axis. Fig. 2 also illustrates the passage of brushes 34 and 36 over the segments of distributor 33 but as such passages do not occur in synchronism with the voltages of line 6, brush 34 is represented in Fig. 2 as engaging with fictitious segments 53a to 53f whereas brush 36 is represented as engaging with another set of fictitious segments of different width 63a to 63j. The sets segments 53a to 53f and 63a to 63f are termed fictitious because it is necessary to a clear explanation of the derivation of the curves of Fig. 2 to illustrate the two brushes as moving at the same speed over different sets of segments, rather than two brushes moving over the same set of segments and at different speeds as above described, to obtain coincidence of the time axes of the contacting of the brushes with the segments and the time axes of the voltage curves. The possible output voltage of winding 11 iinpressed on winding portion 14a. over device 17 is represented by curve 54 comprising successive portions of curves 51a to 511. A voltage represented by such curve is obtained due to the fact that the several control electrodes of device 17 are each periodically energized to permit the associated anode to function and that such anode will function provided that such anode is then positive with respect to the anode previously carrying current and also positive with respect to the associated cathode. During any cycle of the voltage of line 6, such energization of the control electrode may be eiected once by either brush 34 or brush 36, and subsequently by the other of such brushes, the connection of the elec-- trode with battery 28 over the other brush then being without eiiect as, at the time of such ener'- gization, the anode either already carries current or else has become negative with respect to the anode which is then carrying current. Curve 56 is obtained in a similar manner and represents the possible output voltage of winding l2 impressed on winding portion 14h through device 19. Such curve consists of successive portions of curves 52a to 52f representing the voltages of the several portions of winding 12. Each portion of curves 51 is utilized upon passage of brush 34 or 36 over the segment 53 or 63 having the samereference letter whereas the curve 52 utilized is in phase opposition with the curve having the same reference letter as the distributor segment as a result of the particular method of interconnection of the control electrodes of device 17 and 19.

From a consideration of Fig. 2 it appears that the operation of set of anodes 21 over the rising portions of curve 54, occurring during intervals AB and CD, is controlled entirely by brush 34 and that such operation overthe descending portion of curve 54, occurring during interval BC, is controlled entirely by brush 36. Similarly, the operation of anodes 22 is controlled by brush 36 during intervals EF and GH and by brush 34 over interval FG. In Fig. 2, times B and F coincide but such coincidence is not generally obtained. The necessity of energizing each control electrode only momentarily will appear from consideration of curve 51a at time A. At such time brush 34 engages with segment 53e to positively energize control electrode 31c and thereby permit anode 21c to carry current. Such current is subsequently transferred to anodes 21d, 21e, 21f, 21a,

etc. to obtain an output curve 54. Engagement of brush 36 with segment 63c at time K is without effect as anode 21e is already carrying current at such time. If, however, segment 63c was of such width as to remain in contact with brush 36 up to time L, anode 21c, which becomes positive with respect to anode 21e at time M, would then again carry current and such current would not be transferred to anodes 21f, 21a, etc. as such anodes are then negative with respect to anode 21e. Satisfactory operation of the system would therefore not be obtained.

In the further consideration of the. operation of the system, the ripples of curves 54 and 56 will rst be' disregarded and such curves therefore considered as being sinusoidal. Assuming that line 7 is receiving in-phase current from line 6, during time interval NP corresponding to the positive halfcycle of the voltage of line 7, anodes 21a to 21j sequentially become positive with respect to cathode 18 and sequentially carry a current controlled by the action of brushes 34 and 36. Winding portion 14a then receives a voltage represented by the positive portion of curve 54. During the negative half cycle of the voltage of line 7, extending during interval PQ, the anodes of device 17 no longer carry current. The anodes of device 19 then become sequentially positive with respect to cathode 20 at times when brushes 34 and 36 permit such anodes to carry current and winding l2 impresses, on winding 14b, a voltage represented by the positive portion of curve 56. Because of the opposite connection of winding portions 14a and 14b the positive output voltage of winding 12 through device 19 constitutes the negative half wave of the voltage of windings 14 and 16. If line 7 receives lagging current from line 6 the anodes of device 17 become positive with respect to cathode 18 and are capable of carrying current, as a result of the action of brushes 34 and 36, during a time interval RS lagging behind time interval NP. The anodes of device 19 then carry current during anl equal interval ST. Some of the anodes of devices 17 and 19 thus carry current while receiving negative voltages from the associated portions of winding l1 and 12, but such anodes carry current because the associated cathodes are then maintained at a more negative potential than the anodes by the voltage of line 7. If line 7 receives leading current devices 17 and 19 are similarly operated during time intervals which lead intervals NP and PQ.

If line 7 is returning current to line 6, current ows through device 19 during interval NP andv through device .17 during the interval PQ in order that the ilowof current may be opposite in sign to the voltages of winding portions 14a and 14h. The flow of such current is again possible because cathodes 18 and 20 are maintained at negative potentials with respect to the operating anodes by the voltage of line 7.

As the voltages impressed on winding portions 14a and 14h and represented by curves 54 and 56 present certain ripples such voltages do not exactly coincide with the voltage of line 7. The difference between such voltages then appears across the terminals of reactor 29 which may be so chosen as to reduce the ow of ripple current present between lines 6 and 7 to any desired extent. As may be seen in Fig. 2 the voltage ripples occurring simultaneously in curves 54 and 56 are not identical so that the output voltages of devices 17 and 19 are not exactly equal and are of opposite signs at every instant. If line 6 is supplying in-phase current to line 7, device 17 is carrying current during interval NP at a voltage which repeatedly exceeds the negative voltage of device 17 during several non-consecutive time intervals. During such intervals,l device 19 func tions as an inverter to return to winding 12 and winding 8 and line 6, the energy received by device 17 from winding 11 and winding 8 and line 6. An undesired current exchange thus occurs which may be reduced to any desired extent by inserting suitable impedance means in the circuit 'of such currents. Such flow is preferably reduced by reactor 29 inserted between winding 16 and line 7 and which is equivalent to a reactor in the circuit of the exchange currents due to the inductive coupling of windings 14 and 16. Such current exchange may be further reduced or even entirely prevented by controlling the energization of the control electrodes of devices-17 and 19 in such a manner that, at every instant, the output voltage of the device carrying current is less than the output voltage of opposite sign of the device not carrying current. Such adjustment is obtained by means of the taps of resistances 41 and 44 to cause the position of brush 36 to advance or the position ofv brush 34 to lag. It may be seen from Fig. 2 that, if brush 34 is retarded during intervals AB and CD, curve 54 becomes more negative and may be made to become constantly negative with respect to curve 56 taken in inverse sign. During interval FG curve 56 then similarly becomes constantly negative -with respect to curve 54 taken in inverse sign and, consequently, during such interval curve 54 is again negative with respect to curve 56 taken in inverse sign. During interval NP the output voltage of device 17 which is then carrying cur-- vrent is constantly lower than the voltage of device 19 and device 19 cannot return current to1 line 6. Similarly during interval PQ the output voltage of device 19, which is then carrying current, is constantly smaller than the output voltage of device 17 which therefore cannot return current to line 6. The operation of the system .and brushes 57 and 59 replace brush 36.

The flow of in-phase current between lines 6 and 7 is controlled by the phase relations between the voltage impressed on winding 14 from line 6 and theY voltage impressed on winding 16 from line 7. Such phase relation may be adjusted by movement of lever 46 or simultaneous adjustment of the taps of resistances 4l and 44 to simultaneously advance or retard brushes 34 and 36 and to thereby advance or retard the energization of all the control electrodes of devices 17 and 19.

In the embodiment illustrated in Fig. 3 Winding 12 is omitted and the anodes of device 19 are connected with the anodes of device 17 and with the several portions of winding 11. In the present embodiment, cathodes 18 and 20 are connected with the terminals of winding 14 and the mid-tap or neutral point of winding 14 is connected with the neutral point of winding 11. Cathodes 18 and 20 thus being at different potentials, separate energizing means must be provided for each group 'of control electrodes 31 and 32. Control electrodes 3l are generally maintained negative with respect to cathode 18 by a battery 76 through resista-nces such as 77 and 23, and control electrodes 32 are generally maintained negative with respect to cathode 20 by means of a battery 75' over resistances such as 78 and 27. Distributor 33 is replaced by four distributors 48, 50, 58, andl provided with brushes 47, 49, 57 and 59, of which brushes 47 and 49 replace brush 34 Fields 39 and 43 are then preferably both energized from line 7 over resistance 44 to permit simultaneous adjustment of all the brushes by movement of the tap of resistance 44. Such resistance also controls the energization from line 7 of the armature` 64 of a synchronous motor having a eld Winding 66 and operating in synchronism with the voltage of line 7 and driving the brush 68 of a distributor 69 and the brush 71 of a distributor 72. Distributor 69 cooperates with distributors 48 and 58 to positively energize control electrodes 31 positively with respect to cathode 18 by means of a battery 7 3 and over resistance such as 23. Such energization is controlled in such a manner that only one of brushes 47 and 57 receives current from battery 73 during time intervals such as AB, BC, etc. andv a faulty double energization of a control electrode is avoided even if the segments of the distributors are of such Width as'to permit a double energization of a control electrode as described above at the moment M. Similarly, distributor 72 controls the connection between brushes 59 and 49 and battery 74 to control the positive energization of control electrodes 32.

The operation of the present embodiment is similar to that of the embodiment illustrated in Fig. 1. Control electrodes 31 are generally maintained negative with respect to cathode 18 by battery 76 and control electrodes 32 are generally maintained with respect to cathode 20 by battery 75. During time interval AB, control electrodes 31 are sequentially energized from battery 73 over brush 68, 'one segment of distributor 69, brush 47 and the several segments of distributor 48. During interval BC, such control electrodes are sequentially energized from battery 73 over brush 68, the other segment of distributor 69, brush 57 and the several segments of distributor 58. In a similar manner, during interval EF, control electrodes 32 are sequentially energized from battery 74 over brush 71, one segment of distributor 72, brush 59 and the several segments of distributor 6D. During time interval FG such control 'electrodes are sequentially energized from battery 74 over brush 71 and the other segment of distributor 72,V brush 49 and the several segments of dis'- tributor 50. No interference is therefore possible between the action of the several brushes of the distributors and the segments of such distributors may be made of any desired width.

Although but a few embodiments of the present invention have been illustrated and described, it will be apparent to those skilled in the` art that various changes and modifications may be made therein without departing from the spirit of the invention or from the scope of the appended claims.

It is claimed and'desired to secure by Letters Patent;

1.- In a system for transmitting energy between alternating current lines, an alternating current line, a transformer connected with said line, an electron discharge device having anodes connected with said transformer and having controlvoperating independently of the first said means for effecting the continual connection of said source sequentially with the control electrodes of said device at other predetermined moments relal tive to the frequencies of the voltages of said lines.

2. In a system for transmitting energy between alternating current lines, an alternating current line, a transformer connected with said line, an electron discharge device having anodes connected with said transformer and having control electrodes and a cathode, a second alternating current line, a transformer connected with the second said line and connecting the cathode of s'aid device with the first said transformer, a source of control potentials, means responsive to the sum of the frequencies of said lines for controlling the sequential connection of said source with the control electrodes of said device, and means responsive to the difference of the frequencies of said lines and operating independently of the rst said means for cooperatively controlling the sequential connection of said source with the control electrodes of said device.

3.` In a system for transmitting energyl between ,alternating current lines, an alternating current line, a transformer connected with said line, an electron discharge device having anodes connected with said transformer and having control electrodes and a cathode; a second alternating current line, a transformer connected with the second said line and connecting the cathode of said device with the first said transformer, a source of control potentials, means for effecting the continual connection of said source sequen electrodes to such extent as to thereby control the direction of the energy flow between said lines.

4. In a system for transmitting energy between alternating current lines, an alternating current line, a transformer connected with said line, an electron discharge device having anodes connected with said transformer and having control electrodes and a cathode, a second alternating current line, a transformer connected with the second said line and connecting the cathode of said device with the first said transformer, a source of control potentials, means for effecting the continual connection of said source sequentially with the control electrodes of said device at predetermined moments relative to the frequencies of the voltages of said lines, means operating independently of the first said means for effecting the continual connection of said source sequentiallywith the control electrodes of said device at other predetermined moments relative to the frequencies of the voltages of said lines, and means for adjusting the first and the second said means in such sense as to vary the moments of connections of said source with said control electrodes to such extent as to thereby control the intensity of the energy flow between said lines.

5. In a system for transmitting energy between alternating current lines, an alternating current line, a transformer connected with said line, an electron discharge device having anodes connected with said transformer and having control electrodes and a cathode, a second alternating current line, a transformer connected with the second said line and connecting the cathode of said device with the first said transformer, a source of control potentials, means for effecting the continual connection of said source sequentially with the control electrodes of said device at predetermined moments relative to the frequencies of the voltages of said lines, means operating independently of the first said means for effecting the continual connection of said source sequentially with the control electrodes of said'device at other predetermined moments relative tothe frequencies of the voltages of said lines, and means for adjusting the first and the second said means in such sense as to vary the said moments of connections of said source with said control electrodes to such extent as to thereby control both the intensity and the direction of the energy flow between said lines.

6. In a system for transmitting energy between alternating current lines, an alternating current line, a transformer connected with said line, an electron discharge device having anodes connectedwith said transformer and having control electrodes and a cathode, a second alternating current line, a transformer connected with the second said line and connecting the cathode of said device with the first said transformer, a source of control potentials, means for effecting the continual connection of said source sequentially with the control electrodes of said device at predetermined moments relative to the frequencies of the voltages of said lines, means operating independently of the first said means for effecting the continual connection of said source sequentially with the control electrodes of said device at other predetermined moments relative to the frequencies of the voltages of said lines, and means for adjusting the first and the second said means in such sense as to vary the said moments of connections of said source with said control electrodes to such extent as to thereby control the flow of in-phase current between said lines.

7. In a system for transmitting energy between alternating current lines, an alternating current line, a transformer connected with said line, an electron discharge device having anodes connected with said transformer and having control electrodes and a cathode, a second alternating current line, a transformer connected with the second said line and connecting the cathode of said device with the first said transformer, a source of control potentials, means for effecting the continual connection of said source sequentially with the control electrodes of said device at predetermined moments relative to the frequencies of the voltages of said lines, means operating independently of the first said means for effecting the continual connection of said source sequentially with the control electrodes of said device at other predetermined moments relative to the frequencies of the voltages of said lines, and means for adjusting the first and second said means in such sense as to vary the said moments of connections of said source with said control electrodes to such extent as to thereby control the flow of reactive current between said lines.

8. In a system for-transmitting energy between alternating current lines, an alternating current line; a. transformer connected with said line, an electron discharge device having anodes connected with said transformer and having control electrodes and a cathode, a second alternating current line, a transformer connected with the second said line and connecting the cathode of said device with the first said transformer, a source of control potentials, means for effecting the continual connection of said source sequentially with the control electrodes of said device at predetermined moments relative to the frequencies of the voltages of said lines, means operating independently of the first said means for effecting the continual connection of said source sequentially with the control electrodes of said'device at other predetermined moments relative to the frequencies of the voltages of said lines, and means for varying the connection between the second said transformer and the second said line to control the flow of reactive current between said lines.

9. In a system for transmitting energy between alternating current lines, an alternating current line, a transformer connected with said line, an electron discharge device having anodes connected with said transformer and having control electrodes and a cathode, a second alternating current line, a transformer connected with the second said line and connecting the cathode of said device with the rst said transformer, a source of control potentials having a negative terminal thereof continuously connected with said cathode and a positive terminal connectable with said control electrodes, means for `continually connecting the positive terminal of said source sequentially with the control electrodes of said device at predetermined moments relative to the frequencies of the voltages of said lines, means operating independently of the first said means for continually connecting the positive terminal of said source sequentially with the control electrodes of said device at other predetermined moments relative to the frequencies of the voltages ofsaid lines, and means responsive to the frequency of the second said line for variably controlling the moments of the connection of the positive terminal of said source with the first said means.

10. In a system for transmitting energy between alternating current lines, an alternating current line, a transformer connected with said line, an electron discharge device having anodes connected with said transformer and having control electrodes and a cathode, a second alternating current line, a transformer connected with the second said line and connecting the cathode of said device with the first said transformer, a source of control potentials having a negative terminal thereof continuously connected with said cathode and having a positive terminal thereof arranged for connection with the control electrodes of said device, a distributor for continually effecting the connection of said positive terminal of said source sequentially with said control electrodes at predetermined moments relative to the frequencies of the voltages of said lines, and a second distributor operating independently of the first said distributor for continually effecting the connection of the positive terminal of said source sequentially with said control electrodes at other predetermined moments relative vto the frequencies of said lines.

11. In a system for transmitting energy between alternating current lines, an alternating current line, a transformer connected with said line, an

- electron discharge device having anodes connected with said transformer and having control electrodes and a cathode, a second alternating current lineja transformer connected with the second said line and connecting the cathode of said-device with the rst said transformer, a source of control potentials having a negative terminal thereof connected with said cathode and having a positive terminal arranged for connection with the control electrodes of said device, a distributor for effecting the connection of the said positive terminal of said source sequentially with said control electrodes at predetermined moments relative to the frequencies of the voltages of said lines, a second distributor operating independently of the first said distributor for continually effecting the connection of said positive terminal of said source sequentially with said control electrodes at other predetermined moments relative to the frequencies of the voltages of said lines, and a distributor for varying the moments of connection of the said positive terminal of said source with both of the rst said distributors in dependence upon the frequency of the voltage of the second said line.

12. In a system for transmitting lenergy between Valternating current lines, an alternating current line, a transformer connected with said line, a plurality of electron discharge devices each having anodes connected with said transformer and having control electrodes and a cathode, a second alternating current line, a transformer connected with the second said line and with the 'cathodes of said devices, means connecting neutral points in the said transformers, a source of control potential having a negative terminal thereof continuously connected with the cathodes of said devices and having a positive terminal ar'- ranged for connection with said control electrodes,

means for effecting the continual connection of the said positive terminal of said source sequentially with the control electrodes of said device at predetermined moments relative to the frequencies of the voltages of said lines, and means operating independently of the first said means for effecting the continual connection of said positive terminal of said source sequentially with the control electrodes of said device at other predetermined moments relative to the frequencies of the voltages of said lines.v

13. In a system for transmitting energy between alternating current lines, an alternating current line, a transformer connected with said line, a plurality of electron discharge devices each having anodes connected with said transformer and having control electrodes and a cathode, a second alternating current line, a transformer connected with the second said line and with the cathodes of said devices, means connecting neutral points in the said transformers, a source of control potentials, means responsive to the sum of the frequencies of said lines for controlling thev sequential connection of said source with the control electrodes of. said devices, and means responsive to the difference of the frequencies of said lines and operating independently of the first said means for controlling the sequential connection of said source with the control electrodes of said device.

14. In a system for transmitting energy between alternating current lines, an alternating current line, a transformer connected with said line and having a neutral point, a plurality of electron' discharge devices each having anodes 110 connected with said transformer and having control electrodes and a cathode, a second alternating current line, a transformer connected with the second said line and with the cathodes of said devices and having a neutral point, means connecting the neutral points of said transformers,

a source of control potential having a negative terminal continuously connected with the cathode of one of said devices and having a positive terminal connectable with the said control electrodes thereof, a second source of control potentials having a negative terminal continuously connected with the cathode of another of said devices and a positive terminal connectable with the said control electrodes thereof, means for effecting the connection of the said positive terminals of said sources continually with said control electrodes at predetermined moments relative to the frequencies of the voltages of said lines, means operating independently of the first said means for effecting the connections of said positive terminals of said sources continually with said control electrodes at other predetermined moments relative to the frequencies of the voltages of said lines, and means responsive to the frequency of the Asecond said line for varying the moments of connection of said sources of current with the first and second said means.

HEINRICH MEYER-DELIUS. 

